The prevalence of bronchopulmonary dysplasia (BPD) in very low birthweight (VLBW) infants continues to be a significant problem as more and more extremely immature preterm infants survive acute respiratory distress. Traditionally, BPD has been defined as continued requirement for supplemental oxygen at 28 days of life. Because of the extreme immaturity of the survivors, BPD is now defined as the need for mechanical ventilation and/or oxygen at 36 weeks postconceptional age (PCA). Poor growth is the most common morbidity experienced by VLBW infants with BPD. While the cause of this poor growth is multifactorial potential causative factors include inadequate nutritional intake, inefficient nutrient utilization, and inflammation associated with BPD. However, the role of these factors in the poor growth of these infants has not been examined. The purpose of this study is to prospectively characterize relationships among nutritional intake, nutrient utilization, inflammation, and growth in VLBW infants with BPD when compared to VLBW infants at high-risk for BPD (on oxygen at 28 days of life). VLBW infants, appropriate for gestational age, will be studied at 28 days of life, 33 weeks PCA, and 36 weeks PCA. Group differences for study variables will be examined at the three time points. Study variables include growth (growth velocity, arm muscle area, and arm fat area), nutritional intake (kcal/kg/day and grams of protein/kg/day), nutrient utilization (nitrogen balance, serum prealbumin, and serum triglycerides), and inflammation (interleukin-1 ra and tumor necrosis factor). Predictors of growth velocity will also be determined by examining the interactive effects of respiratory disease with nutritional factors, nutrient utilization, and inflammatory factors. Methods to be used for data collection of the study variables include review of the medical record, computer software analyses, collection of body fluids for biochemical assays and bomb calorimetry, and anthropometric measures. Characterizing the determinants of poor growth in VLBW infants with BPD will facilitate understanding of this problem and identify promising areas for nutritional intervention. Further, nutritional intervention may also decrease the severity of BPD. [unreadable] [unreadable] [unreadable]